Hashtags have exploded in popularity over the last few years throughout social media.

So it’s no wonder more brands are staking a permanent claim to some of them by seeking trademark protection.

Nearly 3,000 hashtag trademark applications were filed globally from 2011 through 2015, compared with just seven in 2010, according to recent research from Thomson CompuMark.

“It’s a symptom of the growth of social media,” said Rob Davey, senior director of global services at Boston-based Thomson CompuMark. “Six years ago, most people didn’t know what a hashtag was.”

Now they’re everywhere, and companies understand their viral nature and their influence among social media followers, he said.

Hashtags that have been registered include Kentucky Fried Chicken’s #HowDoYouKFC, Mucinex’s #BlameMucus and Glade’s #BestFeelings, said Alexandra Roberts, a trademark expert and an assistant professor at the University of New Hampshire School of Law.

Hilary Topper, president of Long Beach-based HJMT Public Relations, said she uses hashtags in more than 80 percent of the posts she puts up across social media. “I notice on Instagram when you use certain hashtags that are very popular, your Instagram will grow exponentially in followers,” said Topper, who is also an adjunct professor at Hofstra University in Hempstead.

Topper said she might consider trademarking some of her signature hashtags, particularly those she uses with consistency such as #techinpr. “I incorporate a lot of technology in public relations,” she explained.

Get the Biz Briefing newsletter!

Topper said she encourages her students to tweet with that hashtag after class for extra credit if they learned something they want to share among their followers.

To be sure, the companies that trademark their hashtags want their customers and fans to be using them to give their brand visibility on social media, but at the same time they want to stop their competitors from using them and diverting social traffic away from their brand, Davey said.

Trademarking a hashtag doesn’t stop fans or followers from using it; it simply gives a brand “legal recourse” if a competitor starts using the same hashtag, he noted.

But even that’s not cut and dried.

“The law in this particular area is still developing,” said Michael C. Cannata, a partner in the intellectual property practice group at Rivkin Radler LLP in Uniondale.

A mark comprising or including the hash symbol (#) or the term “hashtag” is registrable as a trademark or service mark only if it “functions as an identifier of the source of the applicant’s goods or services,” according to the United States Patent and Trademark Office (USPTO).

So generally speaking, a hashtag, like a traditional trademark, doesn’t qualify for trademark protection if it’s generic or descriptive, Cannata said.

For example, it’s likely that #hamburgers doesn’t qualify as a unique source identifier when used to market and sell hamburgers, whereas #McDonalds, when used by McDonalds to market and sell hamburgers, likely would, he said.

Although USPTO rules state hashtags may be protected as trademarks, a federal district court recently found hashtags to be merely descriptive and not “source identifiers” as required under trademark law, she said.

“If interpreted broadly by courts, recent court precedent could be used to essentially invalidate trademark protection for hashtag marks on social media,” Campagna said.

Roberts, the law professor, said the district court case in question didn’t involve any registered hashtag trademarks per se, but rather the use of words prohibited under the terms of a settlement agreement.

“It’s something a court said that has been interpreted too broadly by some attorneys and bloggers,” she said.

Her advice in most cases is for companies to register their term or phrase as a trademark without the hashtag symbol (that is, register Acme Widget, not #AcmeWidget), because that offers protection in broader usage, not just when it’s used with the hashtag.

Another factor to consider is how long the hashtag will be in use, Roberts said.

Considering it can take six months to over a year to register a trademark, a marketing campaign could be over by then, Davey noted.

That may be part of the reason some companies end up abandoning their applications, he said. Nineteen U.S. trademark applications for hashtags were abandoned last year and 114 in 2015, according to Thomson CompuMark.

And those are wasted dollars.

The average cost to trademark a hashtag runs from $750 to $1,000, including attorney fees and registration in one class of goods or services, Campagna said.

Also consider that many hashtag applications get rejected.

While U.S. companies have sought protection for more than 1,000 hashtags over the past six years, only 200 of those had been successfully registered as of the end of 2015, Roberts said.

Consider, too, whether consumers will be on your side, she said, pointing to the backlash the ALS Association got a couple of years back when it tried to secure trademark rights to the words “ice bucket challenge” and “ALS ice bucket challenge.” Some people objected to the association attempting to take ownership of what they said started as a grass roots movement.

Trademarked hashtags should have a clear purpose, Topper added. She thinks they can be particularly helpful when promoting an event.

For example, when she runs triathlons or posts about triathlons, she uses the hashtag #trilife.

There are thousands of people who follow that one, Topper said. “People get to know you on a whole different level.”

Fast Fact:

1,042

Number of hashtag trademark applications filed through the end of 2015 in the United States, the most of any country.

Source: Thomson CompuMark

hash·tag

ˈhaSHtagɡ/

noun

A word or phrase preceded by a hash or pound sign (#), used on social media sites such as Twitter to identify messages on a specific topic